Furnace grate



June H8, 11935. F. GRAAFEN 2,095,544

FURNACE GRATE Filed Feb. 25, 1954 certain diiiiculties.

Patented June 18, 1935 FURNACE GRATE Ferdinand' Graafen, Zwickau, Germany f Application February 23, 1934, Serial No. 712,529

In Germany December 24, 1932 6 Claims.

My invention relates to furnace grates.

In the case of the grate described in my Patent 1,975,601, the employment of round stationary tubes between the non-cooled bars involves For this reason the employ-l ment of angular, for example tri-angular, tubes, or of tubes of some other cross-section and having a plain surface has already been proposed in my above VPatent 1,975,601. The emplo-yment of other than round tubes is, however, not expedient, more particularly when the stationary tubes of the grate are connected directly to the boiler. In such acase, the tubes are subjected to the boiler pressure, and consequently it is generally necessary, for reasons of safety, to use round tubes. To eliminate or at least considerably minimize the drawbacks found in the use of such round tubes, is the object of the present invention.

The disadvantage of round tubes is, inter alia, the fact that the upper half of the tube is, usually, subject to greater wear and tear because of the sliding motion of the clinkers moving over it. This is naturally dangerous, more particularly when the grate tubes are joined to the boiler, since in the event of any external mechanical injury to the grate tubesthe risk of an explosion would be imminent. Naturally, too, because of its being rounded off, the upper portion of the tube does not oder a smooth surface to the fuel, and moreover the accurate configuration of the grate openings creates difficulties. More especially, it is hard to keep a fairly large proportion of the fuel from dropping through the grate. The improvements constituting the present invention, eliminate or minimize all these diiiiculties.

According to this invention when round grate tubes are used or tubes of similar cross section, for example polyangular grate tubes, the upper portions of the feed bars disposed between the tubes, substantially those portions lying above the horizontal middle plane passing through the grate tubes, whilst leaving the necessary air spaces; adapt themselves to the periphery of the grate tubes. The feed bars are so designed that the width of the air spaces between them and the. grate tubes gradually increases from the top toward the bottom, in order thereby further toI diminish the risk of such parts as are moved relatively to one another becoming clogged. Additional distinctively new features will appear from the following detailed description of various embodiments, which are shown by way of example on the accompanying drawing, in which (Cl. LZ2-$76) Fig. l is a cross section through two grate tubes and an intermediate uncooled feed bar.

Fig. 2 is a similar cross section through a modification.

Fig. S is a longitudinal section through the embodiment shown in Fig. 2, illustrating how the feed bar is secured.

Fig. 4 is a plan view of a grate embodying this invention, and

Figs. 5 and 6 show two further modifications in cross section.

As described in my Patent 1,975,601, the grate comprises stationary cooled tube elements c extending longitudinally along the grate and cooled by means of a special circulating cooling medium. If desired, the tubes may be connected to the boiler. When connected to a water tube boiler they may be designed to serve as descending or ascending tubes. Lying between every two cooled tubes c and movable to and fro in any desired manner in the longitudinal direction of the grate and parallel to its plane is a feed bar b provided along its upper side with teeth e. All the feed bars need not be moved, as an ample feeding of the fuel may be obtained if only some of said bars are moved. Or the grate tubes may be moved to and fro for the purpose of effecting the feed of the fuel, whilst the bars b remain stationary, in case the grate tubes are not connected to the boiler. Now the feed bars b are so designed that they adapt themselves, more especially above the horizontal middle plane x, to the periphery of the grate tubes. Consequently the upper edge b lies generally opposite a line, on the upper, inner tube quadrant, lying above the horizontal middle plane and on the same side of the vertical middle plane y as the edge b of the feed bar. it isobvious that in this way the upper side of the feed bar b may be of any desired width. By this expedient any portion of the upper side of the tube c may be covered and protected against the direct effect of the fuel. It is thus practically possible for the upper edges b to extend quite close to the vertex of the grate tubes on the vertical middle plane y.

Furthermore, the feed bar b is so designed that, starting from its edge b', the width of the air space b2 lying below said edge b continuously increases. Such a design of feed bar b, when round tubes c are employed, reduces the grinding and abrasive effect of the layer yof fuel and clinkers on the tubes c, and prevents the particles of clinkers from becoming clogged in the space b2, whilst the possibility of any fuel falling through the grate is reduced or considerably minimized. Clinkers passing through the spaces b or even fuel that may get through the spaces b will, because of the increasing width of the space b2, at once drop out underneath..

With regard to the teeth e along the upper face of the feed bars, it may be found suitable to arrange these teeth below the plane of the grate formed by the upper portions of the grate tubes, in order thereby to diminish the heat respectively of the teeth, i. e. to enhance the cooling. lfhe teeth .e may also be narrower than the actual upper face b of the feed bars, in order to prevent the width of the air spaces of the grate from being changed in the event of any expansion of the teeth because of the heat.

As already mentioned,` it is obvious that the stems of the feed bars, b, whilst allowing for the necessary air gaps, may, over any desired range, yadapt themselves to the upper, inner tube quadrants enclosed by the planes :c and y. The greater this range is, the larger will be such por- `tions of the grate tube as are protected from coming into contact with the fuel. 'This may be of great value in the case of very abrasive coals, and also in the case of low grade fuel, in order to diminish the cooling of the bed of coal.

The described embodiment of the feed bar naturally demands a very reliable and firm support, in order that it may be held as strongly as possible I.in the predetermined position against Aswaying from side to side which would give rise to inadmissible space differences. This applies more especially when the feed of the fuel is effected by the to and fro motion of the feed bars b and not by the movement of the grate tubes c. Fig. 2 shows that the feed bars b are 'supported by crossmembers p to which they are \secured by bolts 1'; that the cross members p have fixed thereto and rising therefrom abutment elements i, one disposed to either side of each feed bar b, and that narrow spaces are left between the abutment elements i and the feed `bars b into which intermediate pieces 7c made of sheet metal or the like of variable thickness may 'be inserted, in order to enable adjustment of the lateral spaces between the feed bars b and the grate tubes c. Figure 2 also shows that-the abutment elements i are spaced from the tubes c as indicated at o so that movement of said abutment members with the feed bars and the cross members p does not harm the tubes c. Preferably the abutment elements i are shaped as shown in Figure 2 so that each of them serves as an abutment for two adjacent feed bars. Said abutment elements may, however, be of lany shape desired.

As shown in Fig. 3the feed bars b are provided with shoulders s which lie against the brackets p yand safeguard the xing bolts 1' against the risk of being shorn off in the event of any longitudinal stresses on the feed-bars.

The above described arrangement further possesses the advantage that onlyra comparatively smallv surface of the cooled grate tubes is sub- `jected to the wear and tear due to the layer of fuel moving along said surface, whilst the described design insures an efficient cooling of the Afeed bars.

It will, of course, beexpedient to make the feed bars of a size that their lower edge extends at least as far as the lower edge of the grate tubes, to allow an effective cooling of the lower portion of the bars.A

1t is obvious that the new feed bar may be used to the same advantage in conjunction with tubes of other than round cross-section, for example polyangular. For example, the tubes could also be of half round or approximately round section. Essential in any case is the upward widened cross section or mushroom shape of the feed bars which consequently may also be given a T-shaped cross section, vas isshown in Fig. 6. With this arrangement it is more especially possible to allow the feed bar to overlap in a certain degree in vertical projection the grate tubes, so that the intervening space, when looked at from above, is completely concealed.

The feed bars according to this invention may be smooth on top, since for example in the case of a steep cold-firing grate the fuel bed may be moved forward very easily. On the other hand, teeth may be provided on the feed bars either throughout their respective lengths, or only throughout portions of their respective lengths. As shown in Fig. 5, the rbars b may comprise two parts b3 and b4. For feeding the fuel these two parts b3 and b4 may be moved in any desired manner or may be stationary, if the feeding of the fuel is effected by thewgrate tubes c. l

While Figure 3 illustrates means in the form of a lever Zfor reciprocating the feed bars Without imparting other movements to said bars, any vother suitable means may be employed forA this purpose.

What I claim is: v l. An automatic furnace grate comprisingk lat erally spaced parallel tubes, the top portions of which are of substantially semi-cylindrical shape in cross section and disposed with their apices in a common plane, and solely longitudinally movable grate members between said tubes, the' tops of said grate members being formed of transversely substantially flat surfaces and having at least portions of their transversely substantially flat surfaces disposed inthe same common plane as the apices of the tubes, the upper portions of said grate members extending laterally `outward intol overlying relationship to adjacent side and top portions of the tubes, and said grate membersbeing spaced at all points from said tubes.

2. An automatic furnace grate as set forth in claim l in which the space-s between the grate members and the tubes are of least width their tops and of progressively increasing width downwardly.

3. An automatic furnace grate as set forth in claim 1 in which the grate member between each adjacent pair of tubes is composed of a pair of laterally spaced half-grate sections.

4. An automatic furnace grate as set forth in claim 1 in which the grate members are of T- shaped cross-section.

5. An automatic furnace grate as set forth in claim l including a support upon which the' 

